Image projection apparatus configured to project an image on a road surface

ABSTRACT

Information related to a vehicle can be displayed by projecting an image based on the information on a road surface or the like. An image projection apparatus that projects an image includes: an acquisition unit that acquires information to be displayed; and an image projection unit that projects the image based on the information to be displayed acquired by the acquisition unit.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This non-provisional U.S. patent application is a continuation of U.S.patent application Ser. No. 16/394,607, filed Apr. 25, 2019, which is acontinuation of U.S. patent application Ser. No. 15/565,543 filed onOct. 10, 2017, now U.S. Pat. No. 10,457,199, and claims priority under35 U.S.C. § 119 of Japanese Patent Application No. 2015-213720, filed onOct. 30, 2015, Japanese Patent Application No. 2015-080901 filed on Apr.10, 2015 and international Patent Application No. PCT/JP2016/060613,filed on Mar. 31, 2016, the entire contents of which are herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to an image projection apparatus.

BACKGROUND ART

An image projection apparatus typified by a projector has already beenused in various fields as an apparatus for projecting a desired image inan enlarged manner, and it has been widely used as a display device fora personal computer and a cellular phone in recent years.

Regarding such an image projection apparatus, those listed below havealready been known as prior art techniques particularly related to theuse in a vehicle.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application Laid-Open Publication No.H08-43781

Patent Document 2: Japanese Patent Application Laid-Open Publication No.2004-136838

Patent Document 3: Japanese Patent Application Laid-Open Publication No.2010-26759

Patent Document 4: Japanese Patent Application Laid-Open Publication No.2012-247369

Patent Document 5: Japanese Patent Application Laid-Open Publication No.2014-153868

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Namely, Patent Document 1 described above discloses a projection typedisplay apparatus which uses a vehicle headlight as an external lightsource by disposing an LCD projector, which incorporates no light sourceand is excellent in portability, in front of the vehicle headlight. InPatent Document 2, a first state in which the projector is incorporatedin front of the headlight in the vehicle in advance and a second statein which the projector or the headlight is moved to emit light flux fromthe headlight directly to the outside of the vehicle are realized forsolving a problem of Patent Document 1, and further an embodiment inwhich an image is displayed on a road is disclosed.

Also, an apparatus for vehicle driving support which, in order toeffectively arouse attention of a driver of a vehicle at the time ofdetermination of lane departure, displays information for promotingattention on a road ahead of a vehicle by irradiation means (laser)attached to a headlight part in front of the vehicle is known by PatentDocument 3.

In addition, an apparatus which is provided with a projector asprojection means attached at a front part of a vehicle and projects aroute guide image for guiding the vehicle in a branching direction basedon route information searched by a navigation system on a road surfaceahead of the vehicle, with a setting of a projection angle is alreadyknown by Patent Document 4. Further, an apparatus for vehicle drivingsupport which enables recognition of a place where a vehicle is headingby projecting a drawing pattern made up of target marks and trackinglines on a road surface ahead of the vehicle based on a traveling stateof the vehicle, and thus enables proper driving based thereon is alreadyknown by Patent Document 5.

However, the conventional techniques described above have notnecessarily displayed effectively various types of information necessaryfor traveling of the vehicle.

Thus, the present invention has been made in view of the problems in theconventional techniques described above, and an object thereof is toprovide an image projection apparatus capable of projecting anddisplaying various types of information on a road surface, wall surface,or a vehicle (hereinafter, road surface or the like) based oninformation related to the vehicle such as the traveling state and thelike of the vehicle (mobile body typified by automobile or the like).

Means for Solving the Problems

To solve the problems mentioned above, for example, a configurationdescribed in CLAIMS is adopted. The present application includes aplurality of means to solve the problems and an example thereof is animage projection apparatus that projects an image, and the imageprojection apparatus includes: an acquisition unit that acquiresinformation to be displayed; and an image projection unit that projectsthe image based on the information to be displayed acquired by theacquisition unit.

Effects of the Invention

According to the present invention, it is possible to provide an imageprojection apparatus capable of projecting and displaying information ona road surface or the like based on information related to a vehicle.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a front perspective view of a vehicle which mounts an imageprojection apparatus according to an embodiment of the present inventionand projects an image on a road surface or the like;

FIG. 2 is a rear perspective view of a vehicle which mounts the imageprojection apparatus according to the embodiment of the presentinvention and projects an image on a road surface or the like;

FIG. 3 is a diagram illustrating an overall configuration of a lightcontrol ECU constituting the image projection apparatus;

FIG. 4 is a block diagram illustrating a further detailed configurationexample of the light control ECU and its peripheral elements;

FIG. 5 is a diagram illustrating an example of a configuration of theimage projection apparatus according to the embodiment of the presentinvention;

FIG. 6 is a ray diagram including an image plane of a projector;

FIG. 7 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 8 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 9 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 10 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 11 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 12 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 13 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 14 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 15 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 16 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 17 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 18 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 19 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 20 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 21 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 22 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 23 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 24 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 25 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 26 is a diagram illustrating a specific example of various imagesprojected from a projector onto the road surface based on a relationshipwith vehicle information;

FIG. 27 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 28 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 29 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 30 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 31 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 32 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 33 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 34 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 35 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information;

FIG. 36 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information; and

FIG. 37 is a diagram illustrating a further specific example of variousimages projected from a projector onto the road surface based on arelationship with vehicle information.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

<Arrangement of Image Projection Apparatus>

First, FIGS. 1(A) and 1(B) illustrate a passenger car as an example of avehicle 10 which mounts an image projection apparatus according to anembodiment of the present invention, and as illustrated in thesefigures, a pair of left and right headlights 11 is provided in front ofa main body of the vehicle 10.

In the example of FIG. 1(A), although not illustrated in detail here, alamp as a light emitter is incorporated in each of the pair ofheadlights 11. Also, in the example of FIG. 1(A), a pair of left andright image projection apparatuses described in detail below is mountedin the vehicle (passenger car) 10. Then, image light from the imageprojection apparatuses is projected ahead of the vehicle (passenger car)10 through, for example, transparent window parts. In this example, animage projected on a road surface or the like indicates a current orsubsequent traveling direction to a pedestrian or the like walking nearthe vehicle (passenger car) 10, thereby ensuring higher safety.

FIG. 1(B) illustrates an example in which only one image projectionapparatus is mounted on a front part of a vehicle body. In this case,image light from the image projection apparatus is projected ahead ofthe vehicle (passenger car) 10 through, for example, a transparentwindow part 12 provided at the front part of the vehicle body.

Further, as also illustrated in FIG. 1(A), the image projectionapparatus is mounted also on the bottom and the side of the vehicle(passenger car) 10, and it is thus possible to project a desired imageon the road surface or the like adjacent to both sides of the vehicle(passenger car) 10.

Subsequently, FIGS. 2(A) and 2(B) illustrate a rear side of the vehicle(passenger car) 10 which mounts the image projection apparatus accordingto the embodiment of the present invention, and as illustrated in thesefigures, red tail lamps 13 and 13′ are provided on the rear side of thevehicle body. Further, in the example of FIG. 2(A), although notillustrated in detail here again, a lamp as a light emitter isincorporated in each of these tail lamps 13 and 13′. Also, in theexample of FIG. 2(A), a pair of left and right image projectionapparatuses is mounted, and image light from the image projectionapparatuses is projected behind the vehicle (passenger car) 10 through,for example, transparent window parts.

FIG. 2(B) illustrates an example in which the image projection apparatusis mounted near the roof of the vehicle body. In the example of FIG.2(B), similarly to the example of FIG. 1(B), the image light isprojected behind the passenger car 10 through a transparent window partprovided at a rear end of the vehicle body.

Further, as also illustrated in FIG. 2(A), the image projectionapparatus is mounted also in a side mirror 14, and it is thus possibleto project a desired image on the road surface or the like adjacent toboth sides of the vehicle 10.

In the foregoing, examples in which one or plural (for example, a pairof) image projection apparatuses are mounted on the front, back, left,and right of the vehicle 10 have been described, but the presentinvention is not limited to these, and the image projection apparatusmay be mounted at any location (for example, on the roof or the like) ofthe vehicle 10. Also, the image projection apparatus may be integrallyincorporated in the headlight or the tail lamp. Namely, in the presentinvention, the image projection apparatus may be mounted at any locationas long as a desired image can be projected on the road surface or thelike by the image projection apparatus. In a case where the imageprojection apparatus is integrally incorporated in the headlight or thetail lamp, a light source of the headlight or the tail lamp can be usedalso as a light source for projection.

<Configuration of Light Control ECU>

Subsequently, FIG. 3 illustrates an example of a configuration of anelectronic control unit (light control ECU) mounted in the vehicle(passenger car) 10 described above. As apparent from the figure, a lightcontrol ECU 40 includes a CPU (Central Processing Unit) 41, RAM 42 andROM 43 as storage means, and an input/output device (I/O unit) 44. Thelight control ECU receives information input from a various informationacquisition unit and a communication unit described below via the I/Ounit 44, and controls driving of the headlight 11 and image projectionof an image projection apparatus 500.

Note that the information from the various information acquisition unitincludes, for example, a speed signal indicating a traveling speed ofthe vehicle 10, a signal indicating an engine state (ON/OFF), gearinformation indicating a gear position, a hazard signal notifyingsurrounding drivers of existence of danger, a steering wheel anglesignal indicating a steering angle of a steering wheel, a turn-signalsignal indicating presence/absence of a turn signal (referred to also asa “blinker”) and which of the left and right is lighting/blinking, andfurther lamp lighting information indicating lighting/blinking states ofthe various lamps.

The information from the various information acquisition unit furtherincludes, for example, information from an external light sensor whichdetects light outside the vehicle (illuminance signal, chromaticitysignal, and the like), image information from a camera attached to thevehicle, a signal from a distance sensor which detects a distance toanother vehicle running around the vehicle 10 such as in front of it orother objects, and further a signal from an infrared sensor whichdetects a situation outside the vehicle in the nighttime.

In addition, the information from the communication unit includes, forexample, a GPS (Global Positioning System) signal for determining aposition of the vehicle 10, so-called navigation information that isinformation from a navigation device which performs route guidance andthe like, and further information of inter-vehicle communicationperformed with another vehicle and road-to-vehicle communicationperformed between the road and the vehicle.

FIG. 4 illustrates a further detailed configuration of the light controlECU 40 and its peripheral elements described above. Namely, signals froma direction indicator sensor 51, a steering wheel angle sensor 52 fordetecting an operation angle of a steering wheel (steering angle), ashift position sensor 53, a vehicle speed sensor 54, an acceleratoroperation sensor 55, a brake operation sensor 56, an illuminance sensor57, a chromaticity sensor 58, an engine start sensor 59, and a hazardlamp sensor 60 are input to the light control ECU 40 in FIG. 4. Further,a doorknob sensor 68 for detecting that a driver or a passenger holds adoorknob, a door lock sensor 69 for detecting an open/close state of adoor including a half-opened door, a human sensor 70 for detecting thatthere is no human in a vehicle based on, for example, a load on a seat,and a transmission sensor 71 for detecting a position of a transmissiongear are provided. A signal from a camera 61 is input to the ECU 40 viaan image processing unit 62, and signals from a GPS receiving unit 63and a map information output unit 64 are input to the ECU 40 via acalculation unit 65.

Also, a projector 100 constituting the image projection apparatus 500receives a control signal input from the light control ECU 40 and asignal input from a projection signal output unit 110 (image signalprojected on the road surface or the like) via a control unit 120,whereby projection of an image onto the road surface or the likedescribed below is executed.

In addition, the light control ECU 40 further receives signals inputfrom a headlight sensor 66 and a high/low sensor 67.

<Image Projection Apparatus>

Subsequently, an example of a further detailed configuration of theimage projection apparatus 500 including the projector 100, theprojection signal output unit 110, and the control unit 120 illustratedin FIG. 4 will be described below with reference to FIG. 5.

A projection optical system 501 is an optical system for projecting animage onto the road surface or the like, and includes a lens and/or amirror. A display device 502 is a device which generates an image bymodulating transmitting light or reflecting light, and for example, atransmissive liquid crystal panel, a reflective liquid crystal panel, ora DMD (Digital Micromirror Device) panel (registered trademark) is used.A display device driving unit 503 sends a driving signal to the displaydevice 502, and causes the display device 502 to generate an image.Alight source 505 generates light for image projection, and a highpressure mercury lamp, a xenon lamp, an LED light source, a laser lightsource, or the like is used. A power source 506 supplies power to thelight source 505. Further, the power source 506 supplies necessary powerto each of other units. An illumination optical system. 504 collects anduniformizes the light generated by the light source 505, and emits thelight to the display device 502. A cooling unit 515 cools each part tobe in a high temperature state such as the light source 505, the powersource 506, or the display device 502 by an air cooling method or aliquid cooling method as necessary. An operation input unit 507 is anoperation button or alight receiving unit of a remote controller, andreceives an operation signal input from a user.

An image signal input unit 531 is connected to an external image outputdevice to receive image data input from the external image outputdevice. An audio signal input unit 533 is connected to an external audiooutput device to receive audio data input from the external audio outputdevice. An audio output unit 540 is capable of outputting audio based onthe audio data input to the audio signal input unit 533. Also, the audiooutput unit 540 may output an incorporated operation sound or errorwarning sound. A communication unit 532 is connected to, for example, anexternal information processing device to input and output variouscontrol signals.

A nonvolatile memory 508 stores various data to be used in a projectorfunction. The data stored in the nonvolatile memory 508 includes picturedata and image data prepared in advance for the projection onto theroad. A memory 509 stores the image data to be projected and controlparameters of each unit of the apparatus. A control unit 510 controlsoperation of each of connected units.

An image adjustment unit 560 performs image processing to the image datainput by the image signal input unit 531 and the picture data and theimage data stored in the nonvolatile memory 508. The image processingincludes, for example, scaling processing that performs enlargement,reduction, and deformation of the image, brightness adjustmentprocessing that changes brightness, contrast adjustment processing thatchanges a contrast curve of the image, and retinex processing thatdecomposes the image into light components and changes weighting foreach component.

A storage unit 570 records the image, picture, audio, and various data.For example, the image, picture, audio, and various data may be recordedin advance at the time of product shipment, or the image, picture,audio, and various data acquired from an external device, an externalserver, or the like via the communication unit 532 may be recorded. Theimage, picture, various data and the like recorded in the storage unit570 may be output as a projection image via the display device 502 andthe projection optical system 501. The audio recorded in the storageunit 570 may be output as audio from the audio output unit 540.

As described above, the image projection apparatus 500 can mount variousfunctions. However, the image projection apparatus 500 does notnecessarily have to include all the configurations described above. Theimage projection apparatus 500 may have any configuration as long as ithas a function of projecting the image.

FIG. 6 is a ray diagram of a projector including an image plane. In thisfigure, the image light, which is emitted from the light sourceconstituted of an LED or the like (not illustrated) and transmitsthrough the image display device, passes through a filter and the like,is refracted by various lens systems, and is further reflected inaccordance with the configuration, and is then projected on an imageplane 8 (road surface or the like).

In this manner, in the image projection apparatus 500 described above,the length of the long side of the range of the projection image is10061−542=9519≈9520 mm with respect to the projection distance of 700mm, and thus an unprecedented wide angle of view with the projectionratio of 700/9520=0.07 is realized.

In the foregoing, one image projection apparatus 500 and the projectionoptical system thereof have been described, but as described above, oneor plural (for example, a pair of) projectors may be mounted on thevehicle (or integrally incorporated in the headlights or tail lamps) inthe present invention so that a desired image is projected on the roadsurface or the like. At that time, in a case of the plural (for example,the pair of) image projection apparatuses 500 as illustrated in FIG.1(A) and FIG. 2(A) in particular, the same image may be projected on theroad surface or the like from each of the image projection apparatuses500 (in this case, the same image is displayed on the display device 502of FIG. 5), or different images may be projected from the left and rightimage projection apparatuses 500 and synthesized together on the roadsurface or the like (in this case, an image obtained by dividing thedesired image into left and right is displayed on the display device 502of FIG. 5).

In the foregoing, as the image projection apparatus 500 that projectsthe image on the road surface or the like, the configuration using thetransmissive liquid crystal image display device has been described, butthe present invention is not limited thereto. For example, a reflectiveimage projection apparatus 500 constituted of a micromirror such as aDLP (Digital Light Processing) apparatus and an image projectionapparatus 500 capable of projecting image light from a light modulableplanar light emitting diode via the projection optical system can alsobe used as the image projection apparatus 500 in addition to thatdescribed above. Namely, in the present invention, any image projectionapparatus 500 may be used as long as the desired image can be projectedon the road surface or the like by the image projection apparatus 500.

<Projection Image of Various Types of Information Displayed on RoadSurface or the Like>

Hereinafter, specific examples of various images projected on the roadsurface or the like based on a relationship with vehicle information bythe image projection apparatus 500 described in detail above and mountedon the front and/or rear of the vehicle body in the above-describedmanner will be described in detail with reference to FIGS. 7 to 26.

By the image projection apparatus 500 installed at various locations ofthe vehicle 10 described above, it is possible to display not only astate of the vehicle 10 described above but also an intention of thedriver of the vehicle 10 and the like.

FIG. 7 illustrates an example in which a message is displayed to anothernearby vehicle in a state where the vehicle 10 stops at an intersectionor the like, and a projection image 203 indicating, for example, “pleaseturn right first” is displayed ahead of the vehicle 10 to anotheroncoming vehicle 10′ that displays right turn indication by lighting aturning light in this example.

Note that, regarding the display described above, an image to bedisplayed is stored in advance in the memory 509 (see FIG. 5) that isstorage means constituting the light control ECU, and the image iscalled with a switch or the like provided on a dashboard or the like andis displayed by the image projection apparatus 500. At that time, asalso illustrated in FIG. 10, it is preferable to perform display inorientation opposite to usual orientation so as to make it easy for thedriver of the other oncoming vehicle 10′ to recognize displayedcontents.

In addition, when displaying the message described above, as alsoillustrated in FIG. 8, a display region of the message may be madetrapezoidal or triangular or an arrow 204 indicating a direction of thevehicle that is displaying the message, a vehicle plate number 205, orthe like may be included in a part of the displayed projection image 203so as to make it easy to recognize which vehicle is displaying themessage. Alternatively, although not illustrated here, an animation maybe used.

Meanwhile, as also illustrated in FIG. 9, the message may be transmittedby sounding the contents of the projection image 203 as a voice 250 incombination with the display of the projection image 203.

Further, as also illustrated in FIG. 10, the projection image 203 may bedisplayed ahead of the other vehicle 10′.

Note that, as also illustrated in FIG. 11, the display of the message orthe like described above can be performed to the pedestrian or the likewho is trying to cross the front of the vehicle 10 in the same mannerdescribed above. In that case, the message or the like can betransmitted to the pedestrians or the like more effectively by the voicethrough a speaker provided on the vehicle 10 in addition to the displayof the message 203 or the like. In that case, for example, an audiosignal stored in advance in the memory 509 (see FIG. 5) may be used, orthe voice 250 of the driver of the vehicle 10 may be transmitted througha microphone provided on the dashboard or the like.

Further, regarding the display of the message described above, as alsoillustrated in FIG. 12, it can be considered that a message 206 showingadvertisement contents or the like may be displayed on the road surfaceor the like adjacent to a rear door particularly when the vehicle 10 isa taxi. Alternatively, although not illustrated here, in a vehicle for apublic service such as a bus, a train, or the like, it can be consideredthat the advertisement content message 206 may be displayed in anentrance thereof.

In addition, regarding the display of the advertisement content message206 described above, for example, as illustrated in FIG. 13(A), the ECU40 may be configured to select a plurality of advertisements stored inthe RAM 42 upon reception of a stop signal from the vehicle speed sensor54 illustrated also in FIG. 4 and display the advertisement message viathe image projection apparatus 500. At that time, only one or apredetermined number of different advertisements may be displayed foreach stop, or a plurality of advertisements may be sequentiallydisplayed for a predetermined period of time.

Alternatively, as illustrated in FIG. 13(B), by further providing arouter 1000, the ECU 40 may acquire advertisement information from theoutside of the vehicle 10 by WiFi and display the acquired advertisementcontents.

In addition, particularly when the advertisement is displayed as themessage 206, for example, it is also possible to receive theadvertisement from an advertiser such as a department store close to thevehicle 10 by WiFi by using a configuration illustrated in FIG. 13(B)and display the advertisement contents as the message 206 on the roadsurface or the like as illustrated in FIG. 14.

Further, as illustrated in FIG. 15, instead of the advertisement or thelike described above, information desired by the driver of the vehicle10, for example, “15 km to the destination” (so-called navigationinformation) may be displayed as the message 206 on a sidewalk, sidestrip, road surface, or the like by using the navigation informationfrom the communication unit of FIG. 3. By the display onto the roadsurface or the like including the sidewalk and side strip, it ispossible to prevent false recognition by the driver of the vehicle otherthan the vehicle 10.

Also, regarding the information that the driver wants to know describedabove, as illustrated in FIG. 16, so-called navigation information(traveling direction or distance to the destination of the vehicle 10),vehicle information and alert such as traveling speed and a remainingamount of fuel of the vehicle 10, and further information related to amobile terminal such as a smart phone owned by the driver includingreception of mail may be displayed at the same time as the message 206to be displayed.

In addition, as illustrated in FIG. 17, for example, attentioninformation such as “Attention! There is a disabled vehicle” may bedisplayed as the message 206. At that time, as also illustrated in FIG.17, since the information is attention information to the driver of theoncoming other vehicle 10′, the message 206 is preferably displayedahead of the other vehicle 10′ on the opposite lane. For that purpose,it can be considered that wide-angle display of the image projectionapparatus 500 may be used or the direction of the image projectionapparatus 500 may be changed.

In addition, as the contents to be projected and displayed by the imageprojection apparatus 500 described above, the following can be furtherconsidered.

The driver visually performs various measurements during driving, and asan example of display for assisting such measurements, FIG. 18illustrates a ruler (measure) displayed as a projection image 207 aheadof the vehicle 10. Namely, in this example, since the driver of thevehicle 10 can easily measure a distance to the other vehicle 10′traveling in front of the vehicle 10 (inter-vehicle distance) with theruler (measure) 207 displayed ahead of the vehicle 10, the ruler(measure) 207 contributes to safe driving.

Further, FIG. 19 illustrates a display image 207′ that makes it possibleto easily measure height of a building having a height limit such as abridge or a tunnel (bridge shaped object S) when the vehicle passesunder the building. Note that FIG. 19 illustrates a state where thevehicle 10 traveling toward the object S is viewed from behind.

In the display for the height measurement, from each of the imageprojection apparatuses 500 provided in the headlights provided on bothsides (left and right) on the front of the vehicle 10 (see FIG. 1(A)),an approximately T-shaped bar image 207′ formed by combination of avertical bar and a horizontal bar is projected toward the upper side ofthe road surface in a traveling direction. Note that a pair of the barimages 207′ is set such that backs of the vertical bars are separatedfrom each other at a distance farther than a predetermined distance setin advance (distance>d) and the horizontal bars have a predeterminedheight (for example, a height at which the vehicle 10 can safely pass)at the predetermined distance (d).

As a result, when the vehicle 10 is at the distance farther than thepredetermined distance set in advance (distance>d), the pair of barimages 207′ is displayed to be separated from each other as illustratedin FIG. 19(A). Thereafter, when the vehicle 10 is at the predetermineddistance set in advance (distance=d), the pair of T-shaped bar images207′ is combined to form a cross shape as illustrated in FIG. 19(B). Thehorizontal bars of the “T”-shaped bar images 207′ at this time indicatethe height at which the vehicle 10 can safely pass, and the driver canknow whether or not the vehicle can safely pass by confirming theposition of the horizontal bars of the bar images 207′ in the crossshape. After that, the pair of the T-shaped bar images 207′ is displayedto overlap with each other as illustrated in FIG. 19(C).

Note that it can be considered that the road surface or the like onwhich the vehicle 10 displays various types of information as an imagemay be a road surface or the like that is unpaved and has unevenness onthe surface as illustrated in FIG. 20. In that case, as also illustratedin FIG. 20, a road surface sensor 15 such as a camera (for example, aninfrared stereo camera) is attached in front of the vehicle 10(traveling direction), a state of the road surface or the like (shape,reflectance, and the like) is obtained from an image plane imaged by thecamera, and the image to be projected on the road surface or the like iscorrected based on the result. In this manner, it is possible to displayan image which is corrected based on the shape and reflectance of theroad surface and is excellent in visibility and easily recognizable.

In addition, by using the road surface sensor 15 such as the cameradescribed above, the ECU 40 described above can determine whether theimage is displayed or not displayed in accordance with a flowillustrated in FIG. 21. In the example of FIG. 21, the image projectionapparatus 500 is started (step 210), left and right lane lines of thevehicle 10 are read from the image of the camera to measure a lane widthand detect a road width (step 211), whether or not there is a sufficientroad width to display the image is determined (step 212), the image isdisplayed in a case where it is determined that there is the sufficientroad width to display the image in step 212 (step 213), and the image isnot displayed in a case where it is determined that there is not thesufficient road width to display the image in step 212 (step 214).

Alternatively, by using the road surface sensor 15 such as the cameradescribed above, as illustrated in FIG. 22, a distance to the image 206to be projected is set small in a narrow alley or the like (see FIG.22(A)), and the distance to the image 206 to be projected is set largein a wide road (see FIG. 22(B)). In this manner, an image with excellentvisibility can be displayed. Note that a hatching portion of the figureindicates a projection region of the image projection apparatus 500.

Further, as also illustrated in FIG. 23, by attaching the cameradescribed above to the rear of the vehicle 10, the image of the othervehicle 10′ behind the vehicle 10 obtained by the camera can bedisplayed and projected ahead of the vehicle 10. This will be convenientfor the driver because it is possible to easily confirm the situationbehind the vehicle 10 without looking backward when stopped or the like.

In addition, as also illustrated in FIG. 24, based on the image of thefollowing other vehicle 10′ obtained by the camera attached to the rearof the vehicle 10, the ECU 40 can display warning to the followingvehicle in accordance with a distance to the following other vehicle,traveling speed, and a threshold. Namely, in a case where it isdetermined that the inter-vehicle distance is too short from thetraveling speed, for example, a red arrow is displayed behind thevehicle 10 (see FIG. 24(A)), and in a case where it is determined thatthe distance is not too short but should be noted, for example, a yellowarrow is displayed (see FIG. 24(B)). Further, in a case where it isdetermined that the inter-vehicle distance is sufficient, no display isperformed (see FIG. 24(C)).

In the various examples described above, cases where image light fromthe image projection apparatus 500 is projected on the road surface orthe like around the vehicle 10 have been described. However, the presentinvention is not limited thereto, and it is also possible to performhighlighting to some objects in the projection region of the imageprojection apparatus 500.

As an example, as illustrated in FIG. 25, based on an image signal froma road surface sensor such as the camera attached to the front of thevehicle 10, the ECU 40 detects an obstacle (in this example, a tree) inthe traveling direction (see FIGS. 25(A) and 25(B)). Then, when theimage light is projected by the image projection apparatus 500, theobstacle is selectively displayed by performing highlighting such asblinking only to a portion of the obstacle (in this example, a stem ofthe tree), thereby arousing attention to the driver (see FIG. 25(C)).Note that, in FIG. 25(B), a display range in a vertical direction in thevicinity of the tree by the image light 206 projected from the imageprojection apparatus 500 is indicated by light hatching, and in FIG.25(C), a region in which blinking is turned ON is indicated by darkhatching. Note that, when the ECU 40 determines that an object is notthe obstacle, blinking is turned OFF (see FIG. 25(D)).

Further, as illustrated in FIG. 26, the vehicle 10 can performhighlighting for the pedestrian or the oncoming vehicle 10′ detected byirradiation of infrared light by changing the display color (forexample, red) of only a corresponding portion of a region of the imagelight 206 in a pinpoint manner. As a method for the highlighting,besides the above, brightness of image light to be projected on and/oraround the obstacle may be modulated or the image light may be blinked.Also, an animation or the like may be used. Note that the displayposition of the obstacle highlighting described above performed to theobject (for example, a tree) does not move even when the vehicle 10moves. Further, similar display may be performed not only for theobstacle but also for dangerous objects such as a manhole lid and awheel stop.

In the foregoing, the display of various types of information by theimage projection apparatus 500 (see FIG. 5) has been described as beingperformed as necessary. However, regarding information or the likedisplayed ahead of and behind the vehicle 10 in particular, effectivedisplay thereof cannot be performed when an inter-vehicle distance tothe front vehicle or the rear vehicle is not sufficient. Therefore,although not illustrated here, the display of the projection image maybe performed only when the sufficient inter-vehicle distance ismaintained as a result of the detection by the use of the camera or thesensor described above, and the display may be stopped when theinter-vehicle distance is shorter than a predetermined distance.

Further, details for displaying an image which is corrected based on theshape and reflectance of the road surface and is excellent in visibilityand easily recognizable in relation to FIG. 20 described above will bedescribed below.

First, for distortion (unevenness) of a road surface shape, for example,as also illustrated in FIGS. 27(A) and 27(B), an image 201 in which alattice pattern is inserted in a projection image 200 is projected onthe road surface by the image projection apparatus attached to the frontof the vehicle 10. Then, if distortion of the road surface is detectedby capturing the image ahead of the vehicle by the camera 61 attached tothe vehicle 10 and performing predetermined image processing to theimage by the ECU 40 described above, and the projection image iscorrected in accordance with the detected distortion of the roadsurface, an image that has no distortion and is excellent in visibilityand easily recognizable can be obtained regardless of the distortion ofthe road surface. However, since a predetermined time is required forthat purpose, it is difficult to perform such processing in real time.

Therefore, as also illustrated in a flowchart of FIG. 28, ON and OFF ofthe distortion correction processing described above are switched asappropriate in accordance with the traveling speed of the vehicle. Atthat time, a type of the image to be projected is also included in theswitching condition. This is because since the attention of the driveris directed to interpretation when the display information ischaracters, the display thereof is not considered preferable for safedriving.

Specifically, as also illustrated in the figure, when a road surfaceprojection ON signal is received (S2801), it is determined whether ornot the vehicle is stopped (S2802). As a result, when the vehicle isstopped (“YES”), the distortion correction processing described above isperformed (details thereof will be described below). On the other hand,when the vehicle is not stopped (“NO”), it is further determined whetheror not the traveling speed of the vehicle is lower than a set speed(S2803). As a result, when the traveling speed of the vehicle is lowerthan the set speed (“YES”), the distortion correction processingdescribed above is performed. On the other hand, when the travelingspeed of the vehicle is higher than the set speed (“NO”), it isdetermined whether or not the projection image is characters (or whetheror not characters are included) (S2804). As a result, when theprojection image is characters (“YES”), the road surface projection ONsignal is switched to OFF (S2805). When the projection image is notcharacters (“NO”), switching of the road surface projection ON signal isnot performed (S2806).

In the distortion correction processing executed when the vehicle isstopped (“YES”) in the determination (S2802) and when the travelingspeed is lower than the set speed (“YES”) in the determination (S2802),the image 201 serving as an image for distortion detection in which thelattice pattern is inserted in the projection image 200 described aboveis first projected (S2807). Thereafter, imaging is performed by thecamera described above, and the lattice pattern inserted in theprojection image 200 and a lattice pattern in a screen imaged by thecamera are compared with each other (S2808). Then, when it is determinedthat the distortion of the lattice pattern in the camera imaging screenis larger than a predetermined value (threshold) (“YES”) (that is, thedistortion is too large to be corrected) by the determination (S2809),the road surface projection ON signal is switched to OFF (S2810), thatis, road surface projection is stopped. On the other hand, when it isdetermined that the distortion is smaller than the predetermined value(threshold) (“NO”), correction is performed to a road surface projectionimage (S2811), and the road surface projection is performed withoutswitching of the road surface projection ON signal (S2812). Note thatthe processing described above may be executed by, for example, the CPU(Central Processing Unit) 41 of the light control ECU 40 illustratedalso in FIG. 4.

As apparent from the above, in the above embodiment, basically, theimage is projected only at a speed at which safe driving can be securedwith the inclusion of being stopped, and the display of the image isinhibited particularly when characters are included in the projectionimage. Also, in a case where the distortion on the road surface on whichthe image is projected is too large (amount of distortion>threshold),projection of the image onto the road surface is stopped. In this case,the display of the image is purposely stopped because image distortionin a target person (observer) having a different viewing location alsobecomes larger in the corrected image when the amount of distortion islarge.

Also, brightness and color of the projection image may be made differentfrom the intended ones in some cases due to color of the road surface ora pattern such as a crosswalk. In such a case, there is a possibilitythat intention of the driver who is projecting the image on the roadcannot be correctly transmitted to the surroundings. Thus, in anembodiment also described in detail later, by detecting distribution ofnonuniformity (so-called irregularity) of color and illuminance of theprojection image on the road surface, brightness correction and colorbalance correction are performed at each location on the road surface onwhich the image is projected, so that an image that is excellent invisibility and is easily recognizable is obtained and the image intendedby the driver can be projected on the road surface.

Regarding the distortion (unevenness) of the road surface shapedescribed above, specifically, in addition to the image for distortiondetection illustrated in FIG. 27, that is, the image 201 (see FIG.29(A)) which is projected on the road surface from the image projectionapparatus attached to the front of the vehicle 10 and has the latticepattern inserted therein, an image of full white display (imagecontaining color light of R, G, and B) may be projected on the roadsurface although not illustrated here. Note that the image of full whitedisplay is intermittently projected on the road surface together withthe image 201 in which the lattice pattern is inserted, and may be usedfor the brightness correction as will be described later.

In accordance with the above, based on the imaging screen obtained bythe camera 61 described above (see FIG. 27), distribution of brightnesscan be detected from irregularity in illuminance on the road surface,and illuminance balance of each color can be detected from irregularityin color. Then, by performing the brightness correction and the colorbalance correction based on the detection results in each location onthe road surface on which the image is projected, the image intended bythe driver can be displayed on the road surface. In the above, the casewhere the image of full white display is intermittently displayedtogether with the image 201 in which the lattice pattern is inserted hasbeen described, but the present invention is not limited thereto, and itwould be apparent for those skilled in the art that an effect similar tothe above can be obtained even when, for example, the color light of R,G, and B is sequentially inserted or intermittently inserted.

In addition, when the image projection apparatus described above istilted with respect to the road surface serving as a projection plane ofthe image or displays the image by a so-called oblique projection, thesize of the image is greatly changed and the projection image isdistorted due to a relationship between the image projection apparatusand the road surface, that is, a relative angle (tilt angle) to the roadsurface. For that reason, the image projection apparatus and the roadsurface are preferably parallel to each other.

For example, in a case where the vehicle 10 is parallel to the roadsurface, as also illustrated in FIG. 29(A), the lattice pattern insertedin the projection image is displayed without distortion (originalshape). Meanwhile, as also illustrated in FIG. 29(B), in a case wherethe vehicle 10 is tilted with respect to the road surface, inparticular, tilted to the left side in the horizontal direction withrespect to the traveling direction, the image projected from the imageprojection apparatus and displayed on the road surface is deformed fromits original shape and distorted. Also, in a case where the vehicle 10is tilted to the right side, as illustrated in FIG. 29(C), the image isdistorted similarly. Note that the lattice pattern has been described asthe image inserted in the projection image, but it goes without sayingthat the distortion of the road surface can be similarly detected byusing a rectangular image or a simple rectangular frame instead of thelattice pattern.

Further, as also illustrated in FIG. 30, the vehicle 10 is normallyrequired to be positioned in parallel to the road surface in thetraveling direction (see FIG. 30(A)). However, for example, the vehiclemay be tilted forward (see FIG. 30(B)) or may be tilted backward (seeFIG. 30(C)). Also when the vehicle body is tilted forward or backward inthis way, the image projected from the image projection apparatus anddisplayed on the road surface is reduced backward or enlarged forwardfrom the original shape (rectangle), and distorted by deformation afterall.

Thus, for example, if the rectangular or lattice image pattern describedabove is inserted and the image projected on the road surface is imagedby the camera 61 described above (see FIG. 27) to perform predeterminedimage processing thereto before the image display such as at the startof the vehicle, tilt (tilt in the traveling direction and the horizontaldirection) of the image projection apparatus and further that of thevehicle with respect to the road surface can be detected. If the tiltbetween the image projection apparatus and the road surface is correctedbased on the tilts with respect to the road surface detected in this way(tilts in the traveling direction and the horizontal direction), animage that has no distortion and is excellent in visibility and easilyrecognizable can be obtained. The tilt with respect to the road surfacedetected in this way (tilt in the traveling direction and the horizontaldirection) can be used also for the attitude control of the vehicle bodyby an actuator installed in the vehicle similarly to an auto-levelingfunction of the headlight.

Also, FIG. 21 above illustrates a flow of the determination as towhether the image is displayed or not displayed, executed by the ECU 40by the use of a road surface sensor such as the camera. There, anexample in which it is determined whether or not there is the sufficientroad width to display the image, and the image is displayed in a casewhere it is determined that there is the sufficient road width todisplay the image, whereas the image is not displayed in a case where itis determined that there is not the sufficient road width to display theimage has been described. However, the present invention is not limitedthereto, and display as described below is also possible.

More specifically, for example, in a location where the road width issufficiently wide as also illustrated in FIG. 31(A), by projecting theimage 201 in which the lattice pattern is inserted and comparing anactual image with the projection image by the use of the camera beforethe desired image is projected on the road, existence of the obstacleand walls in left and right front of the road surface can be detected.However, actually, when the detected obstacle such as the walls overlapswith the display image in relation to the size of the image to beprojected as also illustrated in FIG. 31(B), the image may not bedisplayed, or the image to be projected may be reduced as alsoillustrated in FIG. 31(C).

Further, FIG. 32 illustrates a state where the vehicle 10 meets theoncoming vehicle 10′ (obstacle) in a narrow alley. In this case, asindicated by arrows in the figure, a region of the image to be projectedand displayed from the image projection apparatus (see the thick line inthe figure) is limited to a range that can be displayed on the road (seethe dashed line in the figure), or reduced to be displayed.

FIG. 33 illustrates an example of a processing flow in the casedescribed above. First, when the road surface projection ON signal isreceived (S3301), a so-called road width/obstacle detection image suchas the lattice pattern described above is inserted to the projectionimage and is projected on the road surface from the image projectionapparatus (S3302). Thereafter, the image projected on the road surfaceis imaged by the camera, and it is determined whether or not the widthof the imaged projection image is larger than the width of the road(S3303). As a result, in a case where it is determined that the width ofthe projection image is larger than the width of the road (“YES”), theroad surface projection of the image is stopped (OFF) (S3304).

On the other hand, in a case where it is determined that the width ofthe projection image is smaller than the width of the road (“NO”), it isdetermined whether or not there is the obstacle on the road surface byusing the image imaged by the camera (S3305). As a result, in a casewhere there is no obstacle on the road surface (“NO”), road surfaceprojection of the image is executed (ON) (S3306). On the other hand, ina case where there is the obstacle (“YES”), it is further determinedwhether or not the image display can be performed with avoiding theobstacle (S3307). Then, in a case where the image can be displayed withavoiding the obstacle (“YES”), a projection position on the road surfaceis corrected (S3308), and then the road surface projection is executed(ON) (S3309). Note that the processing described above may be performedby, for example, the CPU (Central Processing Unit) 41 of the lightcontrol ECU 40 also illustrated in FIG. 4 above.

In addition, in FIG. 24 above, displaying warning to the followingvehicle in accordance with the inter-vehicle distance to the followingother vehicle, traveling speed, and the threshold has also beendescribed, and its detail will be further described below.

Generally, it is said that a value obtained by subtracting 15 m from thetraveling speed is necessary up to 60 km/h as a safe inter-vehicledistance to stop the vehicle after the detection of the danger.Therefore, the traveling speed of the vehicle is calculated from avehicle speed pulse, and the distance to the following vehicle iscalculated by the camera attached to the rear of the vehicle. In a casewhere the calculated distance is insufficient for a necessaryinter-vehicle distance, a red arrow is displayed as the projection imageto give warning to the following vehicle, and in a case where there isonly a margin of, for example, 10% for the necessary inter-vehicledistance, attention is aroused by a yellow arrow. Also, theinter-vehicle distance to the following vehicle may be detected by alaser radar instead of the camera.

In addition, a stopping distance of a vehicle changes also depending onthe state of the road surface. Generally, 1.5 times the inter-vehicledistance at normal time is necessary during rainfall, and 3 times theinter-vehicle distance at normal time is necessary during road surfacefreezing. Accordingly, setting of the necessary inter-vehicle distancecalculated from the traveling speed described above is preferablychanged in accordance with an ambient environment. For example,detection of rainfall is normally possible by an infrared sensor.Specifically, the detection can be realized by detecting a change inreflection due to adhesion of rain drops to window glass. Also, freezingof the road surface can be detected from specular reflectance of theroad surface. Namely, diffuse reflection components due to unevenness onthe surface are strong in a normal road surface, whereas specularreflection components are strong during freezing because an ice film isformed on the surface. As a result, for example, since specularreflection of the headlight emitted by the oncoming vehicle becomesstrong, a freezing state can be detected by detecting the amount ofreflected light on the road surface. Note that data of thesesafe/attention inter-vehicle distances are stored in the memory as atable in advance.

In the description above, since effective display cannot be performedparticularly when the inter-vehicle distance to the other rear vehicleis not sufficient, the inter-vehicle distance is detected, and theprojection image is displayed only when the sufficient inter-vehicledistance is kept, and the display is stopped when the distance isshorter than the predetermined inter-vehicle distance. However, otherthan that, in a case where there is not the sufficient inter-vehicledistance between the vehicle 10 and the other vehicle 10′ in front ofthe vehicle 10, effective display cannot be performed as alsoillustrated in FIG. 34. Note that FIG. 34(A) illustrates a case wherethere is the sufficient inter-vehicle distance, FIG. 34(B) illustrates acase where the inter-vehicle distance is insufficient, and FIG. 34(C)illustrates a case where there is almost no inter-vehicle distance.

FIG. 35 illustrates an example of a processing flow for implementingwarning to the following vehicle described above. In the figure, first,the inter-vehicle distance between the vehicle and the following vehicleis detected (S3501). Next, the traveling speed of the vehicle isdetected (S3502). Then, presence/absence of rainfall is detected by therainfall sensor described above (S3503). In addition, freezing of theroad surface is detected by, for example, the road surface freezingsensor based on the principle described above (S3504). Thereafter, basedon those detection results, the necessary safe/attention inter-vehicledistances are retrieved from the table described above to set eachdistance (S3505).

After that, it is determined whether or not the inter-vehicle distancedetected above is shorter than the safe inter-vehicle distance set above(S3506). As a result, in a case where it is determined that the distanceis longer than the safe inter-vehicle distance (“NO”), it is furtherdetermined whether or not the distance is shorter than the attentioninter-vehicle distance (S3507). On the other hand, in a case where it isdetermined that the distance is shorter than the safe inter-vehicledistance (“YES”) in the determination (S3506), projection of the warningimage to the following vehicle described above onto the road surface isperformed (ON) (S3510).

Meanwhile, in a case where it is determined that the distance is longerthan the safe inter-vehicle distance (“NO”) in the determination (S3506)but it is determined that the distance is shorter than the attentioninter-vehicle distance (“YES”) in the determination (S3507), theattention image to the following vehicle is projected on the roadsurface (ON) instead of the warning image (S3508). Then, in a case whereit is determined that the distance is longer than the safe inter-vehicledistance (“NO”) in the determination (S3506) and it is furtherdetermined that the distance is longer than the attention inter-vehicledistance (“NO”) in the determination (S3507), display of thesafe/attention information to the following vehicle described above isstopped (OFF) (S3509). Note that the processing described above may beperformed by, for example, the CPU (Central Processing Unit) 41 of thelight control ECU 40 also illustrated in FIG. 4 above.

When an image is to be displayed in addition to the warning to thefollowing vehicle described above, sufficient display cannot be madedepending on the image to be displayed unless there is at least a spacecorresponding to one vehicle. Accordingly, it has been found that it isdesirable that the image is not displayed when the inter-vehicledistances to the front vehicle and the rear vehicle are narrower thanthe image to be displayed. For example, in a case where an image of 4 mwidth is displayed on the road surface 10 m ahead, for example, theimage is observed as a 600 mm square image 10 m ahead from a targetperson with a height of 170 cm. At that time, since the target personcan recognize a size of 30 mm or more 10 m ahead if the target personhas unaided vision of 0.1 or more, it can be seen that it is possible toperform display with the resolution of 16.times.16 or more necessary forcharacter display.

FIG. 36 illustrates an example of processing flow for performing imageprojection on the road surface based on the findings described above. Inthe figure, first, when the road surface projection ON signal isreceived (S3601), it is determined whether or not the image to beprojected is displayed ahead of the vehicle (S3602).

As a result of the determination above, in a case where it is determinedthat the image to be displayed is an image to be displayed ahead of thevehicle (“YES”), next, the inter-vehicle distance between the vehicleand a front vehicle is detected (S3603). Subsequently, it is determinedwhether or not the size of the image to be projected ahead of thevehicle is larger than the inter-vehicle distance detected above(S3604). As a result, in a case where the size of the image is largerthan the inter-vehicle distance (“YES”), projection of the image ontothe road surface is stopped (OFF) (S3605). On the other hand, in a casewhere the size is smaller than the inter-vehicle distance (“NO”),projection of the image onto the road surface is performed (ON) (S3606).

Meanwhile, as a result of the determination above (S3602), in a casewhere it is determined that the image to be displayed is an image to bedisplayed behind the vehicle (“NO”), an inter-vehicle distance betweenthe vehicle and a rear vehicle is detected (S3607). Subsequently, it isdetermined whether or not the size of the image to be projected behindthe vehicle is larger than the inter-vehicle distance detected above(S3608). As a result, in a case where the size of the image is largerthan the inter-vehicle distance (“YES”), projection of the image ontothe road surface is stopped (OFF) (S3609). On the other hand, in a casewhere the size is smaller than the inter-vehicle distance (“NO”),projection of the image onto the road surface is performed (ON) (S3510).

Note that, in the embodiment described above, for example, the latticepattern, the rectangular image, or the simple rectangular frame has beendescribed as the image inserted in the projection image for detectingdistortion of the road surface or detecting the obstacle. In that case,it is preferable to use light in a wavelength band centered on awavelength of 1.4 μm that is light with spectral intensity referred toas “AM1.5”. This is because some of the wavelength components ofsunlight outside the atmosphere are absorbed by components in theatmosphere and do not reach the ground, and some of the spectralcomponents are reduced or eliminated in the spectral intensity referredto as “AM1.5” and the intensity is substantially zero (0) particularlyin the wavelength band centered on a wavelength of 1.4 μm in the nearinfrared region. In other words, this is because the sunlight does notcontain the AM1.5 on the ground where the vehicle runs. Namely, it ispossible to stably obtain road surface condition information withoutbeing affected by the sunlight if the light described above is used.

In addition, the correction of the brightness of the projection imagedescribed above will be described in detail below with reference to FIG.37. Note that, similarly to the above, the processing of the flowchartin this figure may be performed by, for example, the CPU (CentralProcessing Unit) 41 of the light control ECU 40 also illustrated in FIG.4 above.

First, when the road surface projection ON signal is received (S3701),an image for road surface illuminance detection is projected on the roadsurface (S3702). The image for road surface illuminance detection is theimage of full white display described above (image containing colorlight of R, G, and B). Further, during the full white display,nonuniformity (so-called variation) of road surface illuminance isdetected from the image imaged by the camera (S3703). Subsequently, thevariation of detected illuminance (or each value) is compared with apredetermined threshold (S3704).

As a result of the comparison above, in a case where the variation ofilluminance is larger than the threshold (“YES”), it is furtherdetermined whether or not the variation of illuminance is larger than alimit value (S3705). Note that the limit value means a value indicatingthe limit of a range capable of correcting the brightness by the lightsource of the image projection apparatus. As a result, in a case whereit is determined that the variation is larger than the limit value(“YES”), projection of the image onto the road surface is stopped (OFF)(S3706).

On the other hand, in a case where it is determined that the variationis smaller than the limit value (“NO”), illuminance correction of theimage to be projected on the road surface is performed (S3707), and in acase where the variation of illuminance is smaller than the threshold(“NO”) in the comparison above (S3704), projection of the image onto theroad surface is executed (ON) (S3708).

According to the above embodiments, an image that is excellent invisibility and is easily recognizable is obtained, so that it ispossible to project the image intended by the driver on the road surfacereliably and clearly. Further, if the correction of the brightness ofthe projection image described above is performed (for example,sequentially) by using a monochromatic pattern of red (R), green (G), orblue (B) as the image for road surface illuminance detection instead ofthe image of full white display described above, variation of each colorcan be detected, so that color shift correction can also be performed.

Note that the present invention is not limited to the embodimentsdescribed above, and includes various modification examples. Forexample, the above embodiments have described the entire system indetail in order to make the present invention easily understood, and thepresent invention is not necessarily limited to those having all thedescribed configurations. Also, a part of the configuration of oneembodiment may be replaced with the configuration of another embodiment,and the configuration of one embodiment may be added to theconfiguration of another embodiment. Furthermore, another configurationmay be added to a part of the configuration of each embodiment, and apart of the configuration of each embodiment may be eliminated orreplaced with another configuration.

REFERENCE SIGNS LIST

10 . . . vehicle (passenger car), 10′ . . . other vehicle, 11 . . .headlight, 12 . . . window part, 13, 13′ . . . tail lamp, 14 . . . sidemirror, 40 . . . light control ECU, 51 . . . direction indicator sensor,52 . . . steering wheel angle sensor, 53 . . . shift position sensor, 54. . . vehicle speed sensor, 55 . . . accelerator operation sensor, 56 .. . brake operation sensor, 57 . . . illuminance sensor, 58 . . .chromaticity sensor, 59 . . . engine start sensor, 60 . . . hazard lampsensor, 61 . . . camera, 62 . . . image processing unit, 63 . . . GPSreceiving unit, 64 . . . map information output unit, 66 . . . headlightsensor, 67 . . . high/low sensor, 68 . . . doorknob sensor, 69 . . .door lock sensor, 70 . . . human sensor, 71 . . . transmission sensor,100 . . . projector, 110 . . . projection signal output unit, 120 . . .control unit, 500 . . . image projection apparatus, 501 . . . projectionoptical system, 502 . . . display device, 503 . . . display devicedriving unit, 504 . . . illumination optical system, 505 . . . lightsource, 531 . . . image signal input unit, 533 . . . audio signal inputunit, 532 . . . communication unit

What is claimed:
 1. An image projection apparatus comprising: one ormore sensors configured to acquire information relating to a vehicle; aprojector configured to project an image on a road surface, a processorcommunicatively coupled to a navigation device, the one or more sensorsand the projector, wherein the projector is further configured toproject the image based on information acquired by the one or moresensors and information from the navigation device received by theprocessor, and wherein, when the image includes a character image basedon the information from the navigation device and a traveling speed ofthe vehicle acquired by the one or more sensors is greater than apredetermined speed, the projector does not project the image on theroad surface, and wherein, when the image does not include the characterimage based on the information from the navigation device and thetraveling speed of the vehicle acquired by the one or more sensors isgreater than the predetermined speed, the projector projects the imageon the road surface.
 2. The image projection apparatus according toclaim 1, wherein the processor controls the projector to project theimage to different projection positions in accordance with theinformation from the navigation device.
 3. The image projectionapparatus according to claim 2, wherein the projection positions includea driving lane of the vehicle, an opposite lane of the vehicle, and aposition other than the driving lane or the opposite lane.
 4. The imageprojection apparatus according to claim 2, wherein the processorcontrols the projector to project alert information received from thenavigation device to a portion of the road surface of an opposite laneof the vehicle.
 5. The image projection apparatus according to claim 2,wherein the processor controls the projector to project distanceinformation to a destination received from the navigation device to aposition other than a lane of the road surface.
 6. The image projectionapparatus according to claim 2, wherein the processor controls theprojector to project at least one of a traveling direction informationof the vehicle, a traveling speed information of the vehicle, andremaining fuel information of the vehicle to a portion of the roadsurface of a driving lane of the vehicle.
 7. An image projection methodcomprising the steps of: acquiring information relating to a vehicle;communicating with a navigation device; and projecting an image onto aroad surface, wherein the image is based on the information relating tothe vehicle and information received by the navigation device, wherein,when the image includes a character image based on the information fromthe navigation device and a traveling speed of the vehicle is greaterthan a predetermined speed, the image is not projected onto the roadsurface, wherein, when the image does not include the character imagebased on the information from the navigation device and the travelingspeed of the vehicle acquired by the one or more sensors is greater thanthe predetermined speed, the image is projected onto the road surface.8. The image projection method according to claim 7, wherein the imageis projected to different projection positions in accordance with theinformation from the navigation device.
 9. The image projection methodaccording to claim 8, wherein the projection positions include a drivinglane of the vehicle, an opposite lane of the vehicle, and a positionother than the driving lane or the opposite lane.
 10. The imageprojection method according to claim 8, further comprising the step of:projecting alert information received from the navigation device to aportion of the road surface of an opposite lane of the vehicle.
 11. Theimage projection method according to claim 8, further comprising thestep of: projecting distance information to a destination received fromthe navigation device to a position other than a lane of the roadsurface.
 12. The image projection method according to claim 8, furthercomprising the step projecting at least one of a traveling directioninformation of the vehicle, a traveling speed information of thevehicle, and a remaining fuel information of the vehicle to a portion ofthe road surface of a driving lane of the vehicle.